With media processing, there are cases where it is effective to assist a master with an external device, and for expanding the external device, an expansion bus is provided with the master.
Here, the media processing refers to data processing in general, such as audio processing and image processing, the master refers to a device such as a CPU, a microcomputer and the like which performs main control, and the external device refers to a peripheral device such as a coprocessor, an accelerator, a memory and the like which assists the CPU, the microcomputer and the like.
By having the expansion bus and having resources of the external device assigned to the access space, the master can handle the resources of the external device as expanded resources of the master, and thus communication between the master and the external device can be performed at a high speed. As a result, the processing performance of the master can be improved, and it is further possible to facilitate realization of functions of both software and hardware.
Here, the access space is space to which the master can access and to which addresses are assigned for a program access, a data access, an input/output access and the like.
Conventional methods of realizing these accesses include a method where a master is provided with an interface of an expansion bus and accesses an on-chip device via the interface, and further, a method of accessing an external device outside the chip via the interface of the expansion bus of a master and another interface by converting into a protocol of the expansion bus. (See, for example, Patent Reference 1)
Patent Reference 1: Japanese Unexamined Patent Application Publication No. 076151 (p. 15, FIG. 3)